When a person films a scene with a conventional digital video camera, the person can change camera settings based on what is seen through a display of the camera. What the person sees on the display and the video being captured by the camera have the same geometry. With an omnidirectional video camera that captures a spherical scene, changing the camera settings is more complex. An equirectangular projection is often used to show the spherical scene on a rectangular display, similar to how the Earth is projected onto a flat map. The equirectangular projection distorts the spherical scene and the distortion commonly hides issues with the omnidirectional video camera settings.
It would be desirable to implement real-time changes to a spherical field of view.